Detection of Novel Goose Parvovirus Disease Associated with Short Beak and Dwarfism Syndrome in Commercial Ducks

Short beak and dwarfism syndrome among Pekin ducks: First detection, full genome sequencing, and immunohistochemical signals of novel goose parvovirus in tongue tissue

Novel goose parvovirus (NGPV) is continuously threatening the global duck industry, as it causes short beak and dwarfism syndrome among different duck breeds. In this study, we investigated the viral pathogenesis in the tongue of affected ducks, as a new approach for deeper understanding of the syndrome. Seventy-three, 14- to 60-day-old commercial Pekin ducks were clinically examined. Thirty tissue pools of intestine and tongue (15 per tissue) were submitted for molecular identification. Clinical signs in the examined ducks were suggestive of parvovirus infection. All examined ducks had short beaks. Necrotic, swollen, and congested protruding tongues were recorded in adult ducks (37/73, 51%). Tongue protrusion without any marked congestion or swelling was observed in 20-day-old ducklings (13/73, 18%), and no tongue protrusion was observed in 15-day-old ducklings (23/73, 32%). Microscopically, the protruding tongues of adult ducks showed necrosis of the superficial epithelial layer with vacuolar degeneration. Glossitis was present in the nonprotruding tongues of young ducks, which was characterized by multifocal lymphoplasmacytic aggregates and edema in the propria submucosa. Immunohistochemical examination displayed parvovirus immunolabeling, mainly in the tongue propria submucosa. Based on polymerase chain reaction, goose parvovirus was detected in 9 out of 15 tongue sample pools (60%). Next-generation sequencing confirmed the presence of a variant goose parvovirus that is globally named NGPV and closely related to Chinese NGPV isolates. Novel insights are being gained from the study of NGPV pathogenesis in the tongue based on molecular and immunohistochemical identification.

Virus-Like Particles Based on the Novel Goose Parvovirus (NGPV) VP2 Protein Protect Ducks against NGPV Challenge

Novel goose parvovirus (NGPV), a genetic variant of goose parvovirus, has been spreading throughout China since 2015 and mainly infects ducklings with the symptoms of growth retardation, beak atrophy, and protruding tongue, leading to huge economic losses every year. A safe and effective vaccine is urgently needed to control NGPV infection. In this study, virus-like particles (VLPs) of NPGV were assembled and evaluated for their immunogenicity. The VP2 protein of NGPV was expressed in Spodoptera frugiperda insect cells using baculovirus as vector. The VP2 protein was efficiently expressed in the nucleus of insect cells, and the particles with a circular or hexagonal shape and a diameter of approximately 30 nm, similar to the NGPV virion, were observed using transmission electron microscopy (TEM). The purified particles were confirmed to be composed of VP2 using western blot and TEM, indicating that the VLPs of NGPV were successfully assembled. Furthermore, the immunogenicity of the VLPs of NGPV was evaluated in Cherry Valley ducks. The level of NGPV serum antibodies increased significantly at 1-4 weeks post-immunization. No clinical symptoms or deaths of ducks occurred in all groups after being challenged with NGPV at 4 weeks post-immunization. There was no viral shedding in the immunized group. However, viral shedding was detected at 3-7 days post-challenge in the non-immunized group. Moreover, VLPs can protect ducks from histopathological lesions caused by NGPV and significantly reduce viral load in tissue at 5 days post-challenge. Based on these findings, NGPV VLPs are promising candidates for vaccines against NGPV.

Evolution, genetic recombination, and phylogeography of goose parvovirus

Goose parvovirus (GPV) has garnered global attention due to its association with severe symptoms in waterfowl. However, the process underlying the global emergence and spread of GPV remains largely elusive. In this study, we illustrated the evolutionary characteristics of GPVs from a global perspective using phylogenetic analysis, recombination analysis, selection pressure analysis, and phylogeographic analysis. Our findings indicate that GPV and muscovy duck parvovirus (MDPV) diverge into two distinct branches. Within GPV, there are two classifications: classical GPV (C-GPV) and novel GPV (N-GPV), each containing three subgroups, underscoring the significant genetic diversity of GPV. Recombination analysis revealed 11 recombination events, suggesting C-GPV, N-GPV, and MDPV co-infections. Further, phylogeographic analysis revealed that China is an important exporter of GPV and that trade might serve as a potential transmission conduit. Nonetheless, a detailed understanding of its geographic transmission dynamics warrants further investigation due to the limited scope of current genomic data in our study. This study offers novel insights into the evolutionary state and spread of GPV, holding promise for informing preventive and containment strategies against GPV infection.

Parvovirus dark matter in the cloaca of wild birds

With the development of viral metagenomics and next-generation sequencing technology, more and more novel parvoviruses have been identified in recent years, including even entirely new lineages. The Parvoviridae family includes a different group of viruses that can infect a wide variety of animals. In this study, systematic analysis was performed to identify the "dark matter" (datasets that cannot be easily attributed to known viruses) of parvoviruses and to explore their genetic diversity from wild birds' cloacal swab samples. We have tentatively defined this parvovirus "dark matter" as a highly divergent lineage in the Parvoviridae family. All parvoviruses showed several characteristics, including 2 major protein-coding genes and similar genome lengths. Moreover, we observed that the novel parvo-like viruses share similar genome organizations to most viruses in Parvoviridae but could not clustered with the established subfamilies in phylogenetic analysis. We also found some new members associated with the Bidnaviridae family, which may be derived from parvovirus. This suggests that systematic analysis of domestic and wild animal samples is necessary to explore the genetic diversity of parvoviruses and to mine for more of this potential dark matter.

Involvement of Goose Parvovirus in Induction of Angel Wing Syndrome in Muscovy Ducks

Dietary, environmental, and hereditary causes were reported as causative agents of angel wing syndrome in waterfowl. Since 2017, several Muscovy duck flocks at Behira governorate were found to exhibit this syndrome associated with the clinical symptoms of goose parvovirus (GPV) infection. Four strains of goose parvovirus named HS1-HS4 were isolated and identified from diseased ducks at some of these flocks. Phylogenetic analysis revealed clustering of these strains together and within a distinct monophyletic group in relation to GPV strains of Derzsy's disease and short beak and dwarfism syndrome (SBDS). Nucleotide identities with goose parvovirus strain B of Derzsy's disease were 95.7%-96.6%, and with the strain JS1603 of SBDS they were 96.8%-97.4%. However, nucleotide identities with Muscovy duck parvovirus strain FM were 74.1%-74.6%. The disease was reproduced experimentally via oral-route artificial infection with HS1 strain, and both clinical symptoms of goose parvovirus and angel wing syndrome were observed in the artificially infected Muscovy ducks, but with less severity in geese. This study demonstrated clear evidence for induction of angel wing syndrome, at least partially, with GPV infection in Muscovy duck. To the authors' knowledge, this is the first work to mention a viral cause of angel wing syndrome in waterfowl.

Epidemiological Analysis and Genetic Characterization of Parvovirus in Ducks in Northern Vietnam Reveal Evidence of Recombination

In total, 130 tissue-pooled samples collected from ducks in some provinces/cities in north Vietnam were examined for waterfowl parvovirus genome identification. Twenty-six (20%) samples were positive for the parvovirus infection, based on polymerase chain reaction analysis. Of the 38 farms tested, 14 (36.84%) were positive for the waterfowl parvovirus genome. The rate of the parvovirus genome detection in ducks aged 2−4 weeks (37.04%) was significantly (p < 0.05) higher than that at ages <2 weeks (9.09%) and >4 weeks (16.30%). The positive rate on medium-scale farms (9.36%) was significantly (p < 0.05) lower than for small-scale (31.03%) and large-scale (29.73%) farms. The lengths of the four Vietnamese waterfowl parvovirus genomes identified were 4750 nucleotides. Among the four Vietnamese parvovirus genomes, nucleotide identities were from 99.29% to 99.87%. Phylogenetic analysis of the near-complete genomes indicated that the waterfowl circulating in northern Vietnam belonged to the novel goose parvovirus (NGPV) group. The Vietnamese NGPV group was closely related to the Chinese group. Recombination analysis suggested that the Vietnam/VNUA-26/2021 strain was generated by a recombination event. One positive selection site of the capsid protein was detected.

Development and application of a multiplex PCR method for simultaneous detection of waterfowl parvovirus, duck enteritis virus and goose astrovirus

Waterfowl parvovirus, duck enteritis virus and goose astrovirus have become serious pathogens in waterfowl farming. Co-infections occasionally occur, and as a result, it is much harder to rapidly and simultaneously identify several pathogens using conventional PCR. According to the characteristics of the goose parvovirus (GPV) and muscovy duck parvovirus (MDPV) genome sequences, a universal PCR primer was designed using Rep1 as the target gene. The specific detection primers were designed based on the specific conserved regions of UL54 of the duck enteritis virus (DEV) gene and ORF1a of the goose astrovirus (GAstV) gene. The PCR reaction system and conditions were optimized, and the optimal annealing temperature was found to be 56.2 ℃. The volume ratio of the GPV-MDPV, GAstV and DEV primers (20 μM) was 1:4:5. The established multiplex PCR detection method can simultaneously detect GPV, MDPV, DEV and GAstV within one reaction, and be negative for duck Tembusu virus, muscovy duck reovirus, duck hepatitis A virus type 3 and duck circovirus. The method with excellent sensitivity, specificity and repeatability was successfully applied to clinical samples, it is a useful platform for identifing co-infections of GPV, MDPV, DEV and GAstV in waterfowl.

Characterizing two novel goose parvoviruses with different origins

Outbreaks of short beak dwarf syndrome caused by novel goose parvovirus (NGPV) have been prevalent in China since 2015, resulting in a high mortality rate of ducks. Herein we evaluated differences between two NGPV strains: Muscovy duck-origin (AH190917-RP: MD17) and Cherry Valley duck-origin (JS191021-RP: CVD21) NGPV. Both of them showed certain level of pathogenicity to primary duck embryo fibroblasts, Cherry Valley duck embryos and ducklings. CVD21 showed comparatively stronger pathogenicity than MD17. Only CVD21 caused obvious cytopathic effect (CPE), characterized by cell shedding; further, the virus titer of MD17 and CVD21 was 10^2.571 ELD₅₀ (i.e., median embryo lethal dose)/0.2 mL and 10^6.156 ELD₅₀ /0.2 mL, respectively, and the mortality rate of CVD21- and MD17-infected Cherry Valley ducklings was 100% and 80%, respectively. In addition, CVD21 had a greater influence on the growth and development of ducklings. Futhermore, we found that MD17 could infect Muscovy duck embryos and produce lesions similar to Cherry Valley duck embryos, but it could not infect Muscovy duck embryo fibroblasts (MDEFs,) and Muscovy ducklings. MDV21 had no infection to MDEFs, Muscovy duck embryo and Muscovy ducklings. We then sequenced the complete genome of the two isolates to enable genomic characterization. The complete genome of MD17 and CVD21 was 5,046 and 5,050 nucleotides in length, respectively. Nucleotide alignment, amino acid analysis, and phylogenetic tree analysis revealed that MD17 showed higher homology to goose parvovirus (GPV), while CVD21 demonstrated stronger similarity with NGPV. Moreover, the two isolates shared 95.8% homology, with encoded proteins showing multiple amino acid variations. Our findings indicate that Muscovy ducks seem to have played a crucial role in the evolution of GPV to NGPV. We believe that our data should serve as a foundation for further studying the genetic evolution of waterfowl parvoviruses and their pathogenic mechanisms. This article is protected by copyright. All rights reserved.

Molecular Characterization and Pathogenicity of the Novel Recombinant Muscovy Duck Parvovirus Isolated from Geese

Simple Summary

Waterfowl parvoviruses are important pathogens that cause severe disease in young waterfowl. Waterfowl parvoviruses can be divided into goose parvovirus (GPV)- and Muscovy duck parvovirus (MDPV)-related groups. New variant strains can be generated from genomic recombination between different waterfowl parvoviruses and result in new epidemics. Recently, a novel recombinant MDPV (rMDPV) derived from recombination between GPVs and MDPV was reported. This virus caused high morbidity and mortality rates in ducklings and was circulating in waterfowl in mainland China. In this study, a novel rMDPV was isolated in Taiwan from a goose flock that experienced a high mortality. The complete genome of this goose-origin rMDPV was sequenced. Phylogenetic and recombination analyses were performed to elucidate its molecular characteristics. The virulence of this rMDPV was evaluated using experimental infection goose embryos and goslings. This study was the first report showing the pathogenicity of rMDPV in geese.

Abstract

Goose parvovirus (GPV) and Muscovy duck parvovirus (MDPV) are the main agents associated with waterfowl parvovirus infections that caused great economic losses in the waterfowl industry. In 2020, a recombinant waterfowl parvovirus, 20-0910G, was isolated in a goose flock in Taiwan that experienced high morbidity and mortality. The whole genome of 20-0910G was sequenced to investigate the genomic characteristics of this isolate. Recombination analysis revealed that, like Chinese rMDPVs, 20-0910G had a classical MDPV genomic backbone and underwent two recombination events with classical GPVs at the P9 promoter and partial VP3 gene regions. Phylogenetic analysis of the genomic sequence found that this goose-origin parvovirus was highly similar to the circulating recombinant MDPVs (rMDPVs) isolated from duck flocks in China. The results of experimental challenge tests showed that 20-0910G caused 100% mortality in goose embryos and in 1-day-old goslings by 11 and 12 days post-inoculation, respectively. Taken together, the results indicated that this goose-origin rMDPV was closely related to the duck-origin rMDPVs and was highly pathogenic to young geese.

Small but mighty: old and new parvoviruses of veterinary significance

In line with the Latin expression "sed parva forti" meaning "small but mighty," the family Parvoviridae contains many of the smallest known viruses, some of which result in fatal or debilitating infections. In recent years, advances in metagenomic viral discovery techniques have dramatically increased the identification of novel parvoviruses in both diseased and healthy individuals. While some of these discoveries have solved etiologic mysteries of well-described diseases in animals, many of the newly discovered parvoviruses appear to cause mild or no disease, or disease associations remain to be established. With the increased use of animal parvoviruses as vectors for gene therapy and oncolytic treatments in humans, it becomes all the more important to understand the diversity, pathogenic potential, and evolution of this diverse family of viruses. In this review, we discuss parvoviruses infecting vertebrate animals, with a special focus on pathogens of veterinary significance and viruses discovered within the last four years.

Short Beak and Dwarfism Syndrome in Ducks in Poland Caused by Novel Goose Parvovirus

Short beak and dwarfism syndrome (SBDS), which was previously identified only in mule ducks, is now an emerging disease of Pekin ducks in China and Egypt. The disease is caused by the infection of ducks with a genetic variant of goose parvovirus-novel goose parvovirus (nGPV). In 2019, SBDS was observed for the first time in Poland in eight farms of Pekin ducks. Birds in the affected flock were found to show growth retardation and beak atrophy with tongue protrusions. Morbidity ranged between 15% and 40% (in one flock), while the mortality rate was 4-6%. Co-infection with duck circovirus, a known immunosuppressive agent, was observed in 85.7% of ducks. The complete coding regions of four isolates were sequenced and submitted to GenBank. The phylogenetic analysis revealed a close relationship of Polish viral sequences with the Chinese nGPV. Genomic sequence alignments showed 98.57-99.28% identity with the nGPV sequences obtained in China, and 96.42% identity with the classical GPV (cGPV; Derzsy's disease). The rate of amino acid mutations in comparison to cGPV and Chinese nGPV was higher in the Rep protein than in the Vp1 protein. To our knowledge, this is the first report of nGPV infection in Pekin ducks in Poland and Europe. It should be emphasized that monitoring and sequencing of waterfowl parvoviruses is important for tracking the viral genetic changes that enable adaptation to new species of waterbirds.